The present invention relates to a method for setting up a telecommunication link to a person who is in a stationary or mobile, substantially enclosed facility, in particular in a building or in a passenger transport means (e.g., an airplane), inside which there are several communication transmitting terminals operated by a private branch exchange of the facility, whereby a (personal) call number in a telecommunication network, in particular a public one, is assigned to a private telecommunication transmitting terminal of the person, e.g., a radiotelephone. In addition, the invention relates to a corresponding telecommunication system for stationary or mobile facilities each forming a substantially enclosed unit, in particular for buildings or passenger transport means, with a private branch exchange provided inside the facility and able to be called from outside the facility, and with several (internal) communication transmitting terminals provided inside the facility and operated by the private branch exchange, as well as a corresponding telecommunication network.
In general, methods and telecommunication systems are known, for example in the area of office communication, in which calls from a private branch exchange (i.e., a switching center) are forwarded to corresponding private branch exchange terminals, in particular to telephones.
In addition, telecommunication systems with mobile radiotelephone telecommunication transmitting terminals, so-called mobile radiotelephone systems, are known that offer a high degree of mobility. Each subscriber is assigned a personal call number under which he can always be reached, as long as he is in the coverage area of the mobile radiotelephone system.
It is known from German patent DE 196 18 531 C1 to forward a call from a telecommunication network, namely the GSM (Global System for Mobile Communications) mobile radiotelephone network, to a private branch exchange of a private network, namely to a DECT (Digital Enhanced Cordless Telephone) system, if the subscriber is in an enclosed facility, for example inside his office, where the private branch exchange is installed. The private branch exchange described therein is connected via lines with the mobile radiotelephone switching center. The call is rerouted from there together with a call number, the so-called "private branch routing number" to the private branch exchange. This call number, instead of the location data (the so-called "location area identity"), is registered in the subscriber file of the mobile radiotelephone system, and shows how the subscriber can be reached through the private branch exchange in the private network. However, it is not described in DE 196 18 531 how the call is forwarded from the private branch exchange to the communication transmitting terminal (DECT handset) that the subscriber can use. The described call rerouting is not possible if the subscriber has left the coverage area of the mobile radiotelephone system and is in a moving facility, for example in an airplane. Precisely for business customers, for whom airplane trips are an everyday occurrence, the ability to also be reached in the airplane would be desirable, to be able to use the time in the airplane more productively.
At present, only telephone conversations can be transmitted from the airplane to a subscriber on the ground using a credit card or a telephone credit card or calling card, for which telephones are increasingly situated at almost every seat in the airplane.
Thus, for example, U.S. Pat. No. 5,592,539 discloses a telecommunication system in which a call transmitted by a flight passenger from an airplane is received by a ground station and forwarded to a special target station of a ground-supported telecommunication network. For this purpose, a phone station with credit card reader is provided in the airplane, through which the telecommunication takes place with the radio ground station.
In other substantially enclosed facilities as well, such as in ships or trains, and also in facilities such as underground mines, for which telecommunication cannot take place via the public telecommunication network or for which an electromagnetic radio link cannot be made due to interference or for other reasons, e.g., for safety reasons, a person's ability to also be reached within these facilities would be extremely desirable.